David Spero

I guess it is an honorable rite of passage, to become sufficiently prominent in the prepper community so as to attract the attentions of people who are unable to respond rationally to the truths we share, and instead seek to shut us down via illegal means.

So it is with pride as well as a tinge of annoyance that I note we were hacked a while back. For a while we managed to struggle on, but then we had to close down and reinstall from scratch rather than play a game of ‘whack a mole’ with the anonymous adversary.

We’re now coming back online, but it will be a while before we have everything wired up and operating again.

Apologies for the occasional bit of email nonsense that has leaked through over the last few weeks.

Original containers are sometimes a good choice for food storage. But for longest life, often there are better choices.

A large part of prepping is the art of storing provisions and other necessary items in anticipation of a time when they will not be readily available, due to a breakdown in society and its usual services.

Many articles are written about what to store, but very little is written about how to store the things you are collecting. We suggest, and this article explains, that your choice of storage materials is very important.

The best storage container depends on what it is you’re trying to store, and the environment in which you’ll be storing it. For example, you might be okay storing some items in cardboard boxes indoors, but clearly you’d probably never use cardboard boxes for outdoor storage. Or, while you might be okay with storing clothing in plastic containers, you might not want to store food items in the same containers.

Here are some issues to consider when choosing storage containers.

What Are You Protecting For/Against

Some of the biggest reasons for using containers, other than the simple convenience of having everything together, is to protect against one or more external factors.

The most common considerations are

Heat or Cold

Humidity or Water

Oxygen

Light (particularly UV light)

Insects, Pests, Rodents, etc

Grouping items together into convenient and compact collections

Miscellaneous External Factors

Understanding the factors you are protecting against will help guide you towards the appropriate container choices.

Container Life

Do you want a container that will last six months, six years, or six decades? Probably no-one reading this would settle for a six month life, and indeed, most of us would consider six years too short too, but somewhere in the ‘more than six and less than sixty year’ range we’ll likely find a sweet spot.

How do containers age and wear out? Anything that sees the sun will be impacted by the UV rays from the sun. Many natural products will dry out or go brittle or in some other way lose their desirable properties. Plastics will lose their plasticizers and start to crack and break. Metal might rust. Rubber will perish. Wood might rot (or be eaten by termites or chewed through by rodents).

In addition to unavoidable age-related wear and tear, containers might also fail due to things like accidental mishandling and breakage. Drop a glass jar onto a concrete floor and it will probably smash, and you just know that sooner or later, everything made of glass will be dropped – and even if the glass object is already on the floor and therefore unable to be dropped, something will instead drop on it.

Depending on the product you are storing, and where you are storing it, these life related issues will impact to varying degrees.

Container Reusability

Do you want a container than can be reused countless times, or are you happy with a single use container? A tin of food is an example of a container that is single use, a Mason jar is an example of a container that can be reused very many times indeed (albeit with new lids each time if you’re using them as a long life canning alternative.

In the middle between the single use and the virtually unlimited use are containers with a varying number of potential reuses – items with plastic hinges, cardboard flaps, flexible metal detents, plastic bags that will eventually get holes in them, or whatever.

One other aspect of container reusability would be what ongoing use you can get from the material the container is made from. There’s not much you can do with a cardboard container, but with many other materials, you can use them for other purposes. Metal may be able to be worked into other shapes for other purposes. Glass could be melted down and then blown or molded into other shapes, and the same possibly for plastic too.

Container Repairability

Maybe you’ve a container with a limited life, but which can be either readily repaired or have key wear items easily replaced, and so given repeated life extensions. The lids in a Mason jar are an example, gaskets in other lids is another example.

A wooden box can probably be repaired with extra pieces of wood, a hammer and some nails. Maybe super glue can be used to repair other items. Glue – super or ‘regular’ – can also fix some types of breakages in glassware and ceramic items.

And in other cases, cracks don’t even matter too much. A crack in a water container would be a problem, but in a container that is simply storing clothing, not so much.

But in choosing your containers, consider not only their susceptibility to wear and damage, and but also their ability to be repaired, and make sure you have the tools and materials to carry out such repairs.

Permeability

Are you storing something that needs to be fully sealed in (or, a similar concept, have external things fully sealed out)?

Water, for example, ideally should be fully sealed into a container to avoid evaporative loss and environmental contamination. Many food items need to have external things (usually but not exclusively oxygen) fully sealed out.

If so, the permeability of the container becomes an important issue. Many plastics, and obviously most natural products (wood, fabric) are somewhere between moderately and very porous.

If you want impermeability to gases, then you either should look for mylar or nylon type plastics, or glass, or metal.

Interaction with Contents

If you are storing an acidic food, you don’t want it in an aluminum container. If you are storing a liquid, you don’t want it in cardboard (obviously enough). If you are storing water, you don’t want it in a wooden cask or barrel because it will absorb poisonous chemicals and flavors from the wood. You might also not want water in many plastic containers due to the danger of the plasticizers and release agents leaching out of the plastic and into the water.

Environmental Issues

Will the container be inside or outside? Does it need to be non-reactive to water? Does it need to insulate its contents from temperature extremes? Does it need to be impervious to rodents and other creatures? Will it need to be strong to resist wind and other external factors? How about UV issues? Rust? Rot?

Clear or Opaque

Do you need (or would you like) to be able to see the contents inside the container? On the other hand, will light harm the contents of the container?

Container Sizes, Shapes and Weights

Sometimes the size, shape and weight of the container is a relevant issue, other times not so much. A portable product should of course be in containers that aren’t too bulky or heavy to be moved.

If you are space-constrained for storing certain items, you want containers that are efficiently sized (ie usually with square rather than rounded corners and sides) and with little unused storage space inside them.

Multi-Purpose Use

Ideally, you want containers that can be used to hold different things at different times, rather than containers that only work for one thing.

Sometimes it is unavoidable to have containers that can only be used for one thing, because of the nature of the product you store in it. It is hard to re-use a gas container (particularly a plastic one) for drinking water, but there’s no reason why it couldn’t be reused for transporting waste water.

Container Materials

Containers can obviously be made from many different materials. Some of the most common are plastic, glass, metal, and wood or cardboard.

But this list should be further subdivided. Plastics should be divided into permeable or barrier, foodsafe or not, and their ability to resist high/low temperatures and UV. Metal varies from iron to steel to stainless steel, as well as aluminum and more exotic materials. Even wood or cardboard comes in many different grades (food quality or not, painted or not) suitable for different types of applications.

Other materials include fabrics and other natural materials, stone, earth, pottery/ceramic/porcelain, and even concrete.

In addition, containers commonly have a different material for their opening section and/or hinge and/or the seal between their top and bottom.

Two Are Twice as Good as One

Sometimes the ideal approach to storage involves using two containers. For example, putting items first into plastic bags (nylon or mylar) and then putting many of the filled and sealed bags into large multi-gallon plastic pails and sealing the pails.

Even though the pails may not be food-safe, that doesn’t matter. The plastic bag protects the food inside from the pail, while the pail in turn protects the relatively fragile plastic bags from other external environmental factors.

Smaller is Better than Bigger

Which do you think is better – one huge container that is sufficient to hold all of whatever it is you are storing, or multiple smaller containers?

We suggest that having multiple smaller containers is the better choice for several reasons.

First, when you open a container, the life of the item in the opened container may start expiring much more quickly. So if you have a multi-year supply of whatever, but the item will only last three months once the container has opened, you’ll want each container to hold no more than three months of product.

Second, smaller items are more conveniently moved and shifted and managed. You don’t want awkwardly bulky and heavy items that only a strong adult can manhandle – what happens if the strong adult is absent or unwell or indisposed?

A related third factor is one of risk of injury. No-one is likely to risk serious injury if they drop a ten ounce container on their foot, but if they drop a ten pound (or a 100 lb) container on their foot, that might become a life threatening injury (particularly if healthcare is not conveniently at hand).

A fourth factor is to protect against random unexpected container failure causing the loss of your total supply of something. As you of course know and are planning/preparing for, ‘shit happens’ in many different forms. Perhaps one of your containers might have a bad seal or a hairline crack or something in it. If the container has 10% of your supply of whatever inside it, then that’s a disappointing loss; but if it has your entire supply of the item inside, and the failed container has caused the contents to spoil, then that’s a very serious loss.

In this case, the adage to not put all your eggs in one basket is quite literally true!

This also leads to our next point.

Multiple Storage Locations

We suggest not only storing your provisions in multiple containers, but also to store them in multiple locations. If you do this, then events that might cause physical harm to the storage location no longer endanger your entire inventory of stored provisions. Maybe there’s a fire, maybe a flood or even a tornado. Perhaps a tree falls onto the building, or a car crashes into it, maybe there’s a landslide, maybe a satellite falls out of the sky and lands on the storage area! Maybe the zombie horde manage to wrest control of one of your supply dumps from you, maybe anything at all.

No matter what might happen, if you have your stores split over two locations rather than one, your risk is reduced so that, hopefully, a worst case scenario sees you losing only half rather than all your provisions.

Needless to say, be sure that your multiple storage locations are safe and appropriate. You’re just substituting one risk for another if you take some of your provisions and remove them from your protected retreat and instead place them in a shed on the far side of your property, making them vulnerable to anyone passing by.

Containers We Like

We really like glass. It is one of the most unreactive materials, and has an extremely long life assuming it isn’t broken (its biggest weakness). Glass containers with glass stoppers are the best of the best, but you might find yourself needing to accept some other type of seal such as metal or plastic, possibly with or without a rubber or plastic or natural material seal.

You really need to think through the potential challenges of glass breaking. For example, if there’s any chance of earthquakes or other events causing containers to fall off shelving, you need to either ensure the integrity of the shelving or avoid using glass.

For inert products, we like wood and metal, and our favorite metals are either stainless steel (very expensive) or aluminum (a great compromise between strength and weight, but beware of having acids in contact with aluminum). Note also that in some types of fire, aluminum will either melt or even start burning. The average house fire reaches temperatures of 1100°F, and aluminum melts at 660°. Steel on the other hand doesn’t melt until temperatures go above 2500°.

For large liquid storage, either metal or concrete containers seem to be the best solutions.

While we acknowledge the convenience and ubiquity of plastic, we try not to use anything plastic in our long-term storage. Plastic bags – particularly made with a mylar or nylon component – are probably okay, but most other plastics just have too many issues in our opinion.

Many times, with food storage, it is a great idea to add a desiccant, and/or oxygen absorber, to the container of bulk food before sealing it.

Summary

It isn’t enough just to own a lot of provisions and other ‘stuff’. You need to very carefully plan out how and where you store your supplies so as to avoid nasty surprises and problems.

The Baofeng series of radios – our recommended best choice for most prepping purposes.

The General Mobile Radio Service – or GMRS for short – has evolved since its original establishment in quite different form in the 1960s. In 1987 it evolved to essentially its present form, with business use specifically excluded, with a set of eight channel pairs for repeater operation, and seven single channels for non-repeater ‘simplex’ operation.

In 1996 the FCC created a new product – the Family Radio Service or FRS for short. This was sort of ‘GMRS-lite’ and almost literally was squeezed into the ‘gaps’ between GMRS channels. It was designed as a low power service for handheld walkie-talkie type radios only, and unlike GMRS there was no licensing requirement. Anyone could buy FRS radios and ‘play’ with them more or less as they wished.

Because the FRS and GMRS frequencies were sometimes the same and sometimes only very slightly different, radio manufacturers started selling dual-purpose radios that could work either as FRS or GMRS radios. In theory, this was illegal, but in practice, it was so widespread that the FCC chose to do nothing. This created a confusing mix of frequencies and channel numbers, and we previously explained the implications of this in our earlier article explaining the confusion of frequencies between FRS and GMRS.

Finally – 21 years after this all started to become a mess, the FCC has acted to try and clear things up, publishing new rules and frequencies in September 2017, taking effect from late October 2017.

Here now is the new improved official list of channels and an explanation of what each channel can be used for.

Let’s first look at the most relevant list of channels for many of us – the FRS channels.

Table 1 : FRS Channels and Power

Channel Number

Frequency (MHz)

Power (ERP in Watts)

1

462.5625

2.0

2

462.5875

2.0

3

462.6125

2.0

4

462.6375

2.0

5

462.6625

2.0

6

462.6875

2.0

7

462.7125

2.0

8

467.5625

0.5

9

467.5875

0.5

10

467.6125

0.5

11

467.6375

0.5

12

467.6625

0.5

13

467.6875

0.5

14

467.7125

0.5

15

462.5500

2.0

16

462.5750

2.0

17

462.6000

2.0

18

462.6250

2.0

19

462.6500

2.0

20

462.6750

2.0

21

462.7000

2.0

22

462.7250

2.0

Note that all FRS channels require a radio with NFM – ie, 12.5 kHz bandwidth. And, as you can see, the numbering of the channels seems somewhat illogical and out of sequence with the order of the frequencies, as does the different power requirement for the 467 MHz frequencies.

The FCC believes it all makes sense, and helps to fit the FRS frequencies more consistently into the GMRS frequencies too. So let’s now look at the GMRS frequencies.

In the case of GMRS, not only do we show the frequencies and power, we also show what types of GMRS radio can use each frequency, and explain the frequency pairs for repeater use. On the other hand, there are no official channel numbers. Yes, it is quite a lot messier than the simple table above.

Table 2 : GMRS Frequencies and Conditions

(FRS Channel)

Frequency (MHz)

Power (ERP in Watts)

Usage

15

462.5500

50/15

M H R B F

1

462.5625

5.0

M H B

16

462.5750

50/15

M H R B F

2

462.5875

5.0

M H B

17

462.6000

50/15

M H R B F

3

462.6125

5.0

M H B

18

462.6250

50/15

M H R B F

4

462.6375

5.0

M H B

19

462.6500

50/15

M H R B F

5

462.6625

5.0

M H B

20

462.6750

50/15

M H R B F

6

462.6875

5.0

M H B

21

462.7000

50/15

M H R B F

7

462.7125

5.0

M H B

22

462.7250

50/15

M H R B F

–

467.5500

50/15

(M*) (C*) F

8

467.5625

0.5

H

–

467.5750

50/15

(M*) (C*) F

9

467.5875

0.5

H

–

467.6000

50/15

(M*) (C*) F

10

467.6125

0.5

H

–

467.6250

50/15

(M*) (C*) F

11

467.6375

0.5

H

–

467.6500

50/15

(M*) (C*) F

12

467.6625

0.5

H

–

467.6750

50/15

(M*) (C*) F

13

467.6875

0.5

H

–

467.7000

50/15

(M*) (C*) F

14

467.7125

0.5

H

–

467.7250

50/15

(M*) (C*) F

As you can sort of see from this table there are several differences between the GMRS and FRS services. Although the FRS channels 8 – 14 are essentially identical with both services, the FRS channels 1 – 7 are restricted to 2 watts whereas the same GMRS channels allow 5 watts, and the channels 15 – 22 can go up to 50 watts with GMRS service but only 2 watts with FRS.

Plus FRS radios are limited to small handheld radios with fixed antennas, whereas the GMRS radios can have external antennas and be ‘base’ stations with greater power and/or repeaters.

In the power column, we show power of 50/15 for some frequencies. In these cases 50W can be used for mobile, base and repeater radios, but only 15 watts for fixed stations.

So what are these different types of radios? In the usage column we list them as :

B : A Base radio station – a station located at a fixed location that communicates with other base and mobile stations

C : A Control radio station – a base station that communicates through repeaters and can control the repeater

C* : A Control radio station transmitting through a repeater

F : A Fixed radio station – a base station that only communicates with other fixed stations

H : A Handheld portable radio

M : A Mobile radio station (ie in a vehicle)

M* : A Mobile radio station transmitting through a repeater

R : A Repeater radio station – ie one that receives (in this case) on one of the 467 MHz 50 watt channels and automatically/simultaneously retransmits it on the 50W channel that is 5 MHz lower (ie the matching 462 MHz channel)

Note – these definitions are per the FCC Part 95 regulations and seem a bit strange. On the face of it, it seems that handheld units can’t communicate via repeaters, but we suspect this is not actually the case.

Simplifying the GMRS Frequencies

The key difference between the GMRS and FRS frequencies is there are an added 8 GMRS frequencies that are intended to be used only for repeater inputs (in the 467 MHz range).

Otherwise, the frequencies are the same, but power levels are different, and also in the high power channels, GMRS can use wideband FM as well as narrowband FM.

Most of these differences are automatically taken care of in the radio sets themselves.

The strange mix of frequencies sort of makes sense with this graphic illustration published by the FCC.

The FCC’s pictorial explanation of the new FRS and GMRS frequency allocations, which still quite literally leaves gaps or holes in their frequency allocations and reasoning

Summary

The new FRS frequencies and power allocations are much better than the original 14 frequencies and 0.5W power limit. This is a good reason to get new FRS radios, and/or to reprogram your Baofeng or other radios to conform to the new frequencies and power limits.

It is possible the FCC may now start to lightly enforce some of its rules for the FRS and GMRS bands, so it would be wise to generally comply with the new requirements, now they are in effect.

The FCC’s Regulations for FRS and GMRS radio service are contained in Part 95 of their overall regulations.

The FCC have changed some of the rules associated with our use of the FRS and GMRS radio bands. This was primarily to resolve the overlap of GMRS and FRS frequencies, and while the ‘solution’ they’ve adopted is a bit clumsy, it also allows FRS radios to have greater power, which is a good thing.

There are some implications for preppers in the changes – and while it seems the changes are generally good, you’re probably already old enough to realize that the government is seldom here to help us. So read on, then maybe accelerate some of your Comms preparing.

Note that this article, published in November 2017, updates our earlier articles about FRS and GMRS, including an earlier article explaining the formerly confusing mix of frequencies for FRS and GMRS services. You should still read these earlier articles because they contain a lot of general information too, but the specific details of frequencies are now in this new article.

The Key Changes Explained

Formerly FRS radios were limited to a maximum power of 0.5W. Now they can go up to 2W on most (but not all) channels. A four-fold increase in transmission power would typically represent about a doubling in transmit range, although that’s a very approximate statement. If you are already managing to broadcast at maximum line-of-site (eg, over water) then more power won’t get you further. And if you’re currently blocked by buildings and other obstructions, more power won’t cause those obstructions to magically disappear. (We have several articles on radio range – what affects it, and how to maximize it, in our general section on Communications.)

The new rules also strengthen the earlier weak prohibition on voice scrambling devices, but there will be an 18 month transition period where it will still be legal to buy or import radios capable of offering this feature, and probably will not be a future prohibition on using them (in these frequency bands – amateurs have not been allowed to use voice scrambling, ever).

A disappointing non-change was the widely anticipated removal of licensing requirements for the potentially more powerful GMRS radios. On the positive side, the licensing costs have reduced and the FCC is now going to issue ten-year rather than five-year licenses.

In addition, the FCC has formalized the differences between FRS and GMRS radios, and will prohibit the current practice of selling dual purpose FRS and GMRS radios, to make it harder for people to ‘accidentally’ use GMRS frequencies and power levels without a GMRS license. This, and the more powerful FRS radios now permitted, seems to be a solution of general benefit. But there’s a sting in that tail.

Banned Radios?

More significant is the FCC’s ruling that in 18 months, they will ban the import or sale of radios that can be used on the FRS frequencies as well as on other frequencies. We’re not exactly sure what this means, because their explanatory discussion of what they intend seems to be slightly different to the specific wording of the new regulations they have published. For sure, it means that ‘ordinary’ and ‘civilian’ type radios primarily designed for GMRS or for Marine services or for business service can no longer also have FRS frequencies in them.

But what about ‘ham’ radios? Typically, ham radios are designed so they can only transmit on officially permitted ham frequencies – this simplifies the design and construction of the radios, so for cost saving reasons as much as anything else, ham radio manufacturers have tended to only sell radios that generally conform to the permitted ham frequencies. But some of the newer radios, using a different type of internal design (software defined radio) can operate on a broad range of frequencies. In particular, the Baofeng UV-5R and F8HP family of radios work over a very broad range of frequencies, including ham frequencies, commercial and marine frequencies, government frequencies, and both the FRS and GMRS bands. This gives them a huge amount of versatility, and in a SHTF scenario, means you can communicate with many different groups of people and their radios. Add to that an extraordinarily low price and a good range of accessories, and most preppers include a collection of Baofeng radios in their essential supplies. For this reason, we’ve written in some detail about these radios – you can see articles about Baofeng radios and related topics here.

Will the FCC now require that Baofeng radios have a frequency block on the FRS and GMRS bands? While the radios have never been officially approved to operate on those frequencies, until now they have legally been sold including those frequencies, and the radios can generally operate in compliance with the standards imposed on radios working in those two services. Conceivably a prepper might now need to have three radios where previously one was sufficient – an FRS radio, a separate higher powered GMRS radio, and an ‘everything else’ radio (ie the Baofeng).

There are two important aspects to this. The first is that you have until early 2019 before it becomes illegal to import or buy multi-purpose radios, and the second is that any radios you already own or acquire within those 18 months remain legal. On the other hand, if it will become illegal, manufacturers will probably discontinue such radios well in advance, so as not to end up with useless stock. So our suggestion is that you might want to think about adding another one or two (or three or four) Baofeng radios to your inventory while they are still available in their open unrestricted form.

This means that radios such as the Baofeng multi-purpose radios would no longer be available for sale, although any you already have remain ‘grandfathered’ in as legal.

Enforcement Issues

For the last decade or so, the FCC has basically turned a blind eye to activities on the FRS and GMRS bands. The confusion of FRS and GMRS frequencies, combined with radio manufacturers selling combined radios that work on both bands, and at very low retail prices such that anyone and everyone would buy them as ‘toys’ to play with made for a messy situation and the FCC wisely realized there was no way they could prosecute hundreds of thousands of people who bought $25 radios at Wal-Mart and never bothered to read all the fine print about how they could be used and the need to get a FCC license.

But now the FCC has acted to clear up the overlap of FRS and GMRS radios, and has also doubled down on its decision to continue to require licenses to operate on GMRS frequencies, we’d not be astonished to note an uptick in FCC enforcement. And that’s not necessarily a trivial laughing matter to ignore. They can – and sometimes do – levy penalties of up to $20,000 per each and every unauthorized broadcast (here’s a particularly severe case where a guy who did some stupid things on police frequencies, nine times, ended up with a $404,166 fine!).

This is probably the least of your worries in a TEOTWAWKI situation, but until such unhappy time as it comes about, you probably should be reasonably careful to comply with FCC requirements, especially when involved in transmissions to and from your home or retreat. Your chances of being pulled while operating without a license in your car are minimal, unless you are broadcasting personally identifying information, but if you are at a fixed location, or transmitting to someone else at a fixed location, you’d be surprised at how quickly and accurately your location can be plotted.

Summary

We as preppers always have to straddle an uneasy divide. We have no wish to break the law, either before or after some major event and societal collapse, because that needlessly draws attention to ourselves, creates a vulnerability, and accelerates still further the decay of the civil society we are all keen to preserve and benefit from.

But in a potentially lawless future where there’s no longer any prize for being a ‘nice guy’ and possibly no longer any penalty for being a bad guy, we need to make full use of all appropriate tools possible to optimize our survival.

Radios are a case in point. The complex morass of rules created by and enforced by the FCC make sense in normal times, and it behooves us to operation our radio comms in compliance with them. The new changes to the FRS and GMRS services are relevant and important to us.

An example of a signal strength reading from a $25 SDR receiver and using free software on your PC. Essential for testing your Faraday cage.

So you’ve built your Faraday cage, and are ready to fill it with the precious electronic spares you want (need!) to protect against an EMP. Well done.

But there’s one thing you really should do before closing it up and moving on to your next project. Even if you’ve built a simple small and apparently 100% compliant cage, don’t you think you should check and test its effectiveness? You’re placing a huge amount of reliance on this cage and its ability to protect its contents from an EMP, so isn’t it worth spending a bit of time and maybe a few dollars to check that it works as expected.

The interesting thing is that a Faraday cage is not an ‘all or nothing’ thing. It isn’t like putting heavy blackout curtains across your windows and blocking out all the light from outside. It is more like pulling a medium weight curtain across, and then having a searchlight shine on your window from outside. Some light will get through, the key issue is how much.

The same with a Faraday cage. It will reduce the strength of the EMP (the technical term is ‘attenuate’) but it won’t block it out entirely. So how much attenuation will it provide, how much do we need, and how do we measure it?

How Much Attenuation is Desirable

First, how much attenuation do you need? More is always better than less, but after a point, you reach a realm of vanishing returns and unnecessary extra protection. We suggest you should look for 40 dB (dB = decibel) of attenuation, and ideally over 50 dB.

What do these numbers mean? If you reduce something by 30 dB, you have reduced its power 1,000 times. If you reduce it by 40 dB, you’ve reduced its power 10,000 times. If you think to yourself ‘every ten dB adds another zero to the number of times the signal is reduced’ then you’d be correct.

So, after the lesson, the test. How many times would the strength of an EMP be reduced if it had a 50 dB attenuation? Please tell me that you answered 100,000 times. Clearly that’s a lot, isn’t it, and probably it is enough. Let’s see why we say that.

A strong EMP effect will induce voltages in the order of 50,000 volts/meter (it is difficult for EMPs to exceed this – anything higher than that and the sky sort of ‘short circuits itself’, although there are rumors of some ‘super EMP’ weapons that have found a way to create higher voltages). If we reduce 50,000 by 40 dB, it is down to a trivial 5 volts/meter, and if we take it down by 50 dB, it is down to a hard to measure 0.5 V/m (ie 500 mV/m).

To put this into context, a strong radio signal ranges between 1 – 100 mV/m. So after about 56 dB of attenuation, the strongest probable EMP is no more harmful than a strong radio signal – ie, totally utterly harmless. And we’ve at least 10 dB of overload above that and probably 20 dB before there needs to be significant concern about EMP damage to electronic circuits that are switched off.

Measuring Attenuation – Decibels and Frequencies

There is an interesting complicating factor. An EMP has a mix of different radio frequencies, and Faraday cages block different frequencies by varying degrees. In general terms, the higher the EMP’s frequency, the less the attenuation.

So that begs the question – exactly what frequencies are likely to be found in an EMP? The short answer is ‘all of them’, which isn’t very helpful, is it! A better answer is ‘most EMPs are expected to concentrate most of their energy in frequencies below 100 MHz’. To put 100 MHz into a meaningful context, it is right in the middle of the FM dial.

That is actually a bit of welcome good news. The lower the frequency, the better most Faraday cages work at blocking it. So if we test the cage at 100 MHz, we know that its blocking will be better at lower frequencies and that the 100 MHz result is getting close to a ‘worst case’ scenario.

There are a number of ways you can do this test.

Test 1 – The Phone Test

This is the easiest of all the tests, and is also the least valuable, but as a quick rule of thumb test, it can tell you if your Faraday cage might fail, although it probably can not tell you if the cage for sure will succeed (testing for failure and testing for success are surprisingly different things).

Take your cage and your cell phone to somewhere with good cell phone coverage. Ideally, go somewhere where the cell phone is receiving on the approx 850-900 MHz range of frequencies, rather than on the 1900 MHz set of frequencies. You can do this by using the excellent antennasearch.com website – put in your address, and then download all the different transmitters it finds close to you (chances are you’ll be surprised at how many there are!). Use the tower map to find a tower belonging to the wireless service you use and which has only 900 MHz not 1900 MHz transmitters on it, then go to it to test.

This is more difficult than it sounds, and probably you’ll compromise by simply testing at home. That is okay, but to get a helpful result, make sure that your cell phone has four or five bars of signal strength before putting it in the cage.

Close up your cage, and call your phone. Maybe you’ll be able to hear the phone ringing inside. If the phone rings, you know your cage is probably not working well.

If the cage material insulates the sound, simply check to see if the phone reports a missed call when you open it up again. If it shows a missed call, that suggests your cage isn’t fully optimized.

Your cell phone can probably receive signals down to a signal strength of about -115 dBm. You can probably get your phone to tell you the strength of the signal it is receiving if it is an Android or iPhone – here’s a good article on how to do so, and if you’re interested, this article tells you more.

So if your phone was showing a signal strength of -85 dBm before it went into the cage, and it didn’t ring, you know that the cage is probably providing at least 30 dB or more of attenuation (ie dropping it from -85 to -115 or more) but you don’t really know how much more than the 30 dB it is giving you. And with only 30 dB of attenuation, that is close to a ‘failure’ so not hearing the phone ring, in this case, isn’t as positive as you’d think.

And if your phone is showing -55 dBm before going into the cage and still rings, you know the cage is providing less than about 60 dB of attenuation, but you don’t know how much less. At 60 dB of attenuation, having the phone ring can still be considered a ‘success’, although you mightn’t think so by hearing the phone ring

So you need to interpret your phone results with care and caution. You may be getting either false positive or false negative results; it helps if you know the signal strength the phone was receiving before going into the cage, and what the minimum signal strength is your phone will work on.

Plus, you are ‘torture testing’ your cage by checking its effectiveness at 900 MHz or 1900 MHz. There is unlikely to be significant energy in an EMP at those sorts of frequencies, and the cage will probably offer better protection at lower frequencies.

So let’s now look at a slightly more helpful test.

Test 2 – Two Walkie Talkies

If you can walk inside your cage, go in with a walkie-talkie and have someone outside with a second one. Close the cage up and see if you can communicate between the two of you. If you can, that is suggesting a ‘fail’; if you can’t, that is suggesting a ‘pass’ for your cage.

The walkie talkies ideally should be on the MURS frequencies (about 150 MHz). If you don’t have MURS capable radios, then FRS or GMRS (about 450 MHz) will work in a pinch, as well. CB radios would not give as meaningful a result.

If you can’t walk inside your cage, that’s okay too. In slightly simplistic terms, a cage not only blocks external signals from traveling into the cage, but also blocks internal signals from traveling out. So all you need to do is use a rubber band to hold down the transmit key on a walkie-talkie, put it into your cage and close it up, and see if you are receiving any signal on the other walkie-talkie outside.

Note that walkie talkies sometimes have a ‘timer’ that stops their transmitting after a period of time. Check that, when you reopen the cage, the walkie-talkie inside is still transmitting.

This is a good test with fewer ambiguities than the cell phone test. You can be reasonably certain that if you can’t get a walkie-talkie signal through your cage, then it will block an EMP too.

But if the radios can still communicate with each other, is that necessarily a fail? It depends on how much the signal strength has dropped. If one of the radios has an accurate S-meter on it, this is helpful. In theory, each ‘S unit’ on an S-meter represents a signal strength change of 6 dB, so you would want to see a 7 S unit movement or more between the two signals. However, particularly, with inexpensive walkie talkies, they either have no S meter at all, or the S meter they do have is woefully inaccurate.

It is not prudent to rely on S meter values, even on quite expensive receivers.

Test 3 – Walkie Talkie and SDR

Good news. You can actually do a very accurate test of the efficiency of your cage with very inexpensive items. You want to have a walkie-talkie to place inside your cage, and use a SDR to measure the signal strength, accurately, on the outside.

For the walkie-talkie; if you don’t have a bunch of them already, get a Baofeng UV-5R. While it is some years since we reviewed these lovely units, and while there have been later models released, the standard UV-5R, at a cost of around $30 each on Amazon, still remains an unbeatable value and excellent performer. Tune it to a frequency around 145 – 155 MHz, it doesn’t really matter what. You could tune it down to a lower frequency (they work down to 136 MHz) but best to keep it around the radio’s ‘sweet spot’.

But what is an SDR? The acronym stands for ‘Software Defined Radio’. Instead of a traditional radio with knobs and dials and everything, a SDR is a computer device – often in the form of a USB stick that connects into your computer, and which is then controlled by a computer program rather than by old-fashioned ‘analog’ controls.

These are amazing gadgets that can be had for as little as $25 (actually, you can get ones for even less than $25, but this specific $25 SDR is the best performing/best value unit until you start going way over $100). Download the free SDR+ (pronounced ‘SDR Sharp’) software from here, plug the unit into your computer, and run the SDR+ software. (If you have a Mac, you could try this free software.)

SDR radios have many uses for preppers, particularly as broad-band multi-mode scanners. We’ll write more about them in future articles.

Tune to the same frequency as your HT (walkie talkie), make sure that you’ve zeroed out the RF gain and turned off the AGC, and you can get information on exactly the dBm signal strength that is being received by putting the cursor on the top frequency display. If the signal is too strong – ie, you don’t get a nice single peak on the SDR’s display, but a whole series of peaks and a general lifting of all the frequencies being monitored, take the antenna off the SDR and maybe replace it with just a very short piece of wire.

Then stick the HT into the cage, close it up, and you’ll see exactly the drop in signal strength. Maybe you go from +5 dBm to -40 dBm, or something else. In such a case, clearly the cage has provided you with 45 dB of attenuation. How easy (and accurate) is that!

In this screen shot (a larger view of the image at the top of the article), you can see that the display is monitoring a signal at 145.330 MHz, with a signal strength of +2.5 dBFS (forget about the FS, it means ‘relative to full scale’ – a concept which is not relevant to our needs). That is a very powerful signal, and as you can see, it ‘stands up’ a long way above the random background ‘noise’ (the other data tells us the background noise is 56.2 dB below full-scale, and so in total, there is a separation of 58.7 dB between the background noise and the measured signal) and some other weak signals that you see small peaks for.

After getting your ‘out of cage’ reading, which this is, you then simply put the radio in the cage and get a second ‘in the cage’ reading. The difference between the two dBFS readings is the amount of attenuation, and hopefully it is reporting more than 40 dB.

Summary

You shouldn’t assume your Faraday cage is giving you the protection you need and are relying on. Fortunately, there are some relatively easy ways to test its functionality.

Ideally, you should be getting more than 40dB of attenuation from your cage.

So there you are, browsing through eBay or the local Craigslist; maybe you’re walking through a second-hand store or at a garage sale, but somehow, you find yourself looking at a tempting bargain. Should you buy it?

Or maybe, instead, you’ve simply decided that the best way to make your dollars go further is to buy as much used gear as possible. You already know that a used car that has dropped in price down to one-quarter of new can still have many years and tens of thousands of miles of good life in it – surely the same is true of electronics, too?

Well, yes and no. There are several things to consider when looking at buying used electronics such as radio gear, computers, and pretty much all other ‘gadgets’.

Pricing

The first surprising point is that while some electronic items drop in price very quickly, others do not. A 5 – 10 year old computer – well, that’s probably going to be available at pennies on the dollar. But a 5 – 10 year old radio transceiver? Not so much.

Indeed, something as old as a 15 or 20 year old radio might still be selling for a high percentage not only of its original price but of what you’d pay for comparable gear, new, today.

There’s an interesting implication of this, and the answer is perhaps not what you’d expect. If a radio still costs 50% of more of its new price when it is 15 – 20 years old, does that mean that it still has half its life to go? Does this suggest that radio gear has a 30 – 40 year life?

Another consideration that is increasingly becoming relevant – with the growing availability of low-priced Chinese gear, you sometimes find yourself with a choice between a ‘brand name’ product (ie primarily the big three Japanese brands – Icom, Yaesu and Kenwood) that sells new for perhaps $750, which sells if 15 years old for, say, $500, or a brand new Chinese product with similar capabilities, for $250. How does it make sense to consider the $500 item when the brand new name brand item, several models newer and ‘better’ is not very much more, and a similar and possibly better new Chinese product is half the price?

Plus, whereas used cars have a number of different services that publish valuations to help you understand if you’re getting a good value or not, there’s nothing comparable for used electronics. This of course works both ways – maybe you’re getting a tremendous value, but maybe you’re being offered something shamefully overpriced.

Age vs State of the Art vs Fashion vs Value

Some things have technological obsolescence long before they actually wear out. Computers and cell phones are good examples of this, although both product lines seem to be ‘maxing out’ and we’re all buying computers and phones less regularly than we used to. But, do you really want to buy a ten-year old computer at any price? Do you really want it with an old-fashioned CRT VGA monitor, some sort of Pentium processor, a mere 1 GB or so of disk, and so on?

We suggest that this is false economy and not a good choice. Remember, after TEOTWAWKI, there isn’t going to be a repair store to go to, there aren’t going to be online help forums, and there won’t be spare parts.

We might buy a ten-year old refrigerator or vehicle, but no way would we buy a ten-year old computer. We wouldn’t even accept one, for free. With many electronic items, the ‘state of the art’ has changed so much as to make the older product truly obsolete, and useless at any price. It isn’t even useful for spare parts. What use is incompatible memory; an old and power-hungry screen with such low resolution as to be useless, a hard drive with an out-of-date interface, etc?

The trap in that scenario is buying something that is very inexpensive, but also very useless.

Sometimes the latest ‘state-of-the-art’ features truly are valuable and worth paying extra for. Before you settle for something ten or more years out of date, make sure you know what you’re missing out on. And even seemingly ‘old fashioned’ technologies like radio transmitters and receivers are changing (quite drastically due to digitization) and with much/most electronic gear, the newer model with newer features can truly be worth paying extra for.

Another factor that encourages faster replacement than is indicated by simple measurement of things wearing out is fashion. Mercifully this afflicts women more than men (such as me!), but marketeers even try to encourage us to change our clothing long before it is worn out. Wide lapels or short. Bell-bottom flared trousers or straight/narrow/skinny. And so on. ‘This season’s colors’ – gack! Cars used to be sold on an annual model refresh cycle, that has slowed down a bit too, but generally we all buy clothing – and probably cars too – long before the economic and effective life of the item we are replacing has expired.

The opportunity in that scenario is buying something that still has a lot of good working life left, and which has been valued lower than it is worth simply because it isn’t fashionable.

Opportunistic Buying – Yes or No?

By nature, many of us preppers are acquisitive and tend to eagerly accept anything we can get, particularly if it is free. Anything we have space to store and which might possibly be of some value in the future seems like a no-brainer to accept – no downside to taking it, and who knows what upside, right?

We don’t entirely disagree with that concept, and if you saw the cartons and closets full of junk we have, clearly we’re as bad as anyone else! We laugh at fashion – we just dig far enough back in our closet to find clothing that matches the ‘new’ fashion but from the previous time it was in fashion.

But there is a danger, if/when you buy opportunistically, that you start confusing irrelevant actions with important results. Which is better : To have a double garage you can no longer drive either car into because it is full of old junk that you’ll never actually use, even in an extreme Level 3 situation? Or to have just a couple of cartons of essential items that you will use and need, for sure? To buy $1000 worth of junk that maybe is worth much more if you ever have a need for it, but then to lack the money to buy a $1000 item that you will definitely for sure need?

The garage full of junk obscures the fact you might be missing some essential items. And your ability to repurpose the junk in your garage will also be reduced after TSHTF, because you can’t just go to the local hardware store or wherever/whatever to get an extra piece of two of stuff to modify/repair/adapt the junk item to a practical purpose.

You’ll also have very much less spare time; you’ll need to focus your time on productive essential tasks, and the same will be true of your friends and neighbors (and, excuse us for saying this, but who knows how many of them will survive through the stressful times and still be available as resources for you to turn to).

A useless thing is a useless thing, no matter how little you pay for it.

Why is it Being Sold?

If you like hearing lies, ask any seller of anything ‘Why are you selling this?’.

Now sometimes you don’t need to ask the question, because the answer is sadly obvious. The item is little better than junk (at least in the seller’s mind); maybe it doesn’t work, maybe the seller doesn’t even know what it is, or maybe it is no longer needed (eg a baby’s crib). You see a lot of that sort of stuff at garage sales.

But when you’re looking at higher value items that apparently still have value and life left in them, it is a question to ask, even if the answer is meaningless.

Nine times out of ten, the answer will be a lie, and the tenth time, it will probably be an obscured truth. For example, if the seller says ‘I got the newer model’, then the obscured truth might be ‘This one failed and I had to replace it’.

If you think about yourself, two things are probably usually true. You only replace things when you uncover limitations or problems with them, and you generally keep things that are working well, even if you buy additional or replacement units. You’re not alone in this approach – many other people do exactly the same, and only sell items when they absolutely for sure have no remaining value, or when something bad has happened to them.

So, know this : There’s almost always a ‘bad’ reason why anyone is selling anything. You may or may not uncover that reason, but expect there to be one.

There are additional lies that specifically relate to electronic gear being sold. For example, ‘it has a nearly new battery’ and ‘it hasn’t been used much’. Unless you see a new battery still sealed in its original packing and with a recent manufacturing date stamped on it, you probably should plan on replacing the battery (or at least buying a new one as spare). The same goes for ‘I’ve just replaced all the tubes’ – unless you can test the tubes, consider them all as near the end of their life – and even if the tubes were recently replaced, you don’t know how much remaining life there is in the new tubes.

Some people might also tell you it has recently been ‘re-capped’ – that all the electrolytic capacitors have been replaced. Ask to look inside the unit and see for yourself – do they look new or old? Is the soldering fresh and bright, or older and duller, like everything else? Has every electrolytic been replaced, or just the ‘easy to get at’ ones?

You might also been told ‘it has just been serviced by an authorized dealer’ – only accept that claim if you see the invoice and perhaps, if it is a high value item, you’ll even want to call the dealer and confirm that the work order was to ‘check/overhaul everything and make the unit in perfect like-new order’ and see if the dealer has any notes about issues they found and weren’t authorized to repair. Just because you see a $200 invoice that says ‘repair item’ doesn’t mean that every fault with the item was repaired, or that the repair used new replacement parts, etc.

One more lie that some people can tell with a straight face – ‘I haven’t used it for a while, but last time I did it worked perfectly’. If it can’t be fully operated and demonstrated to you prior to you buying it, you should prudently expect the worst.

Bartering and Negotiating

It should go without saying that you should avoid paying the initial asking price on anything that is being offered for sale. Experts at negotiating deals consistently tell us two things – the first is that the first person to name their price loses the negotiation, and the second is that the magic phrase to use is, and say this slowly and thoughtfully, in an uncertain but helpful tone, ‘What is the best price you’d accept for this?’.

If you think about it, the two pieces of advice are two sides of the same coin, aren’t they. By asking the guy to name his best price, he is the first person to put a number out there. You might be able to talk the guy down further, but for sure, you know there’s no way you’ll have to pay extra above that revised asking price!

Once you’ve done most of the dickering over price, see if you can then switch to another line of bargaining. ‘Could you throw in the —- as well?’ – see if you can have him include something else as well.

Maybe try to negotiate a deal for two items, but then, when you’ve beaten the guy down as low as you can for a ‘quantity discount’ for the two or more items, then look disappointed and say ‘Thanks for trying to help me with this. Unfortunately, the price is over what I could afford for all the items we’re talking about. But, I tell you what. I’ll take the xxxx off your hands for $—-.’ That way, you’ve managed to get a quantity discount for only buying one thing!

Another thing. Sometimes you might be able to trade something you have and are willing to dispose of as part or full exchange for the item the other guy is selling. This can be the best deal of all. If you have something you don’t need but the other guy wants, and he has something he doesn’t need but you want, then it ends up with you both giving away something unimportant and getting something of value in return. A ‘win-win’ deal like that is the best of all.

If you don’t really need something, but would be willing to buy it at a bargain price, a useful strategy is to say to the seller ‘I’d be interested in helping you out by taking your xxxxx off your hands, but the thing is, I didn’t come here today looking to buy one, and I don’t really need it. So I could only justify it to my wife it I got it at a heck of a deal. What say you try selling it to anyone else for the best price you can for the rest of the day, and I’ll come back at closing time, and if you still have it, then I’ll give you $— for it?’.

This makes best use of the pressure of time in the deal. If you’re going to a one day sale event somewhere, at the start of the day, there’s a rush of buyers all wanting to get the best bargains, and the sellers are optimistic that the rush will continue and they’ll get their asking price for everything they have. But that first rush doesn’t last long at all, and half way in to the day, it is over, and sellers are starting to gloomily think to themselves ‘no-one has even shown any interest in my xxxxx at all’ and they’re starting to think they’ll need to pack up unsold items and take them back, instead of the cash they might have sold them for.

By giving the seller a fair chance to sell the item for more, and by making the point that at the end of the day, no-one else is likely to be buying it, you might be able to negotiate a very low price such as to make it sensible to buy the thing you don’t really need or want.

One of the things that gives us the most troubled sleep of all is the risk of, and outcomes from, an EMP attack on the US. In case you’re not fully up to speed on this draconian danger, we discuss EMP attacks – what they are, how fearsome their impacts would be, and how easy they are to stage – in several articles here.

Our sense is that the danger of an EMP event is steadily increasing. To be blunt, the world is becoming an increasingly unfriendly place, and with growing sophistication of both nuclear weapons and their associated delivery systems (ie missiles) by both North Korea and Iran (as well as other countries that aren’t being quite so public about their actions) and some threats that translate quite clearly to ‘if we need to, we’ll use an EMP device to bring your country to its knees’, the thought of an EMP attack is far from impossible to countenance. At the same time, our lives continue to become more and more dependent on electronics for everything we do.

We are increasingly of the opinion that it is prudent to maintain a spare set of essential electronic items in a protective Faraday cage so that if/when an EMP occurs, you have a backup set of equipment to turn to.

One consideration when planning for this. There is no point in keeping backup equipment that relies on other equipment or services owned/operated by other people/organizations, unless you are certain that these other parties will also be able to continue to provide services after an EMP. For example, what is the point of having a backup cell phone if all the cell towers and network infrastructure by the wireless companies is fried by EMP, and also if the cell phones owned by most of your contacts are also fried!

So, with that as introduction, let’s continue…..

As you may already know, and as our other linked articles explain, an EMP attack destroys electronics by creating high voltage surges in them. These high voltage surges are induced by electromagnetic radiation – a fancy way of saying ‘radio waves and similar type things’. Because the voltage is induced by electromagnetic radiation, there is no need for electronic objects to be connected to anything – they wirelessly ‘receive’ these voltage surges, whether they want to or not, the same way that radios receive radio waves, televisions receive broadcast tv signals and cell phones receive phone calls.

Worst of all, perhaps, switching off your devices doesn’t protect them from these voltage surges. You can unplug your devices and take the batteries out, but they are still at risk of being ‘fried’ by the electromagnetic radiation caused by an EMP device.

Note that while EMP effects are a problem to your at-home electronics, solar flares and storms are not a problem, assuming your electronics are not plugged into utility power (or possibly internet connections). Unplugged, and battery operated, devices will not be affected by the different type of EMF radiation generated in a solar storm.

Back to EMP risks and counter-measures. There are several ways to protect your electronics. Some are impractical, at least for us, because they involve a redesign and ‘hardening’ of the electronic items when they are designed and built.

Others are impractical for other reasons, such as burying our electronics at least 10 ft underground.

The easiest approach for most of us would be to select items we wanted to protect and save for use after an EMP, and place those items inside a special type of container, known as a Faraday Cage. This device is named after the English scientist Michael Faraday, the discoverer of electromagnetic fields, and deemed the inventor of these protective containers, back in 1836, although in truth it was Benjamin Franklin who first observed the properties of such containers, in 1755.

If you think about it, there’s something slightly strange about using a device first observed 260 years ago, to protect against a modern type of risk only developed 60 years ago. But progress is a funny thing, right?

What is a Faraday Cage

The chances are you may have already experienced the protective effects of a Faraday cage, and without even realizing what was going on. If you’ve ever been on a plane that was struck by lightning, the reason you lived to tell the tale – and the reason the plane wasn’t destroyed – is because the entire plane acts as a super Faraday cage, protecting itself and its contents.

A Faraday cage is simply an electrically conductive metal container that completely surrounds its contents. When electromagnetic radiation reaches the container/cage, it has two choices for what it does next – it can either travel through the container, and thereby exposing the contents inside to its damaging effects, or it can travel around the outside of the container on its conductive exterior.

It is ‘easier’ for the radiation to travel on the conductive exterior, and indeed, the conductive exterior works so as to in effect compel the radiation to take this route rather than to go inside, through, and outside the container again.

So, think of a nice old-fashioned metal biscuit tin with a close-fitting lid. Instant Faraday cage! Any type of metal container, of most reasonable shapes and sizes, will work perfectly well as a Faraday cage.

Tight mesh metal screens have sometimes been used as radio frequency shielding too. We don’t recommend this approach because the wave-length of the energies released by an EMP tend to be shorter, and therefore might be small enough to ‘fit through’ the holes in the mesh. Plus, unless you have excellent electrical connections at each node where the screen mesh running in one direction intersects with the screen mesh running at sort of right angles to it, you’ll end up with invisible gaps in your radiation blocking. Best to play it safe and stick to solid metal.

As implied by the comment on screens and their lesser effectiveness, nothing is an absolute in this world, and a Faraday cage – even made out of thick 100% copper, won’t necessarily eliminate 100% of all the radiation. A little bit might still ‘leak’ through into the inside. But a well constructed Faraday cage will reduce the radiation inside itself to perhaps one millionth or less of the level of the radiation outside the container, and that is probably sufficient reduction (the technical term is ‘attenuation’) as to reduce the radiation level from a dangerous level that risks the integrity of your devices to a trivial level that poses no threat to them.

Faraday Cage Construction 1 – The Need for a Total Metal Enclosure

Don’t think that a container that has metal on some of its surrounding surfaces – maybe even as many as five of the six sides of a cube shape – will protect its contents. A typical example of that would be some sort of metal container with a plastic lid.

Such a shape is not a cage at all – rather it could become a ‘wave guide’ which might funnel radiation through it and maybe even concentrate it in some essentially unpredictable manner.

The container needs to have as close to complete metal coverage as possible. Small holes are okay, but the electromagnetic radiation can travel through holes and other cuts and slits in the container. The bigger the hole, the more radiation that can go through it, exactly as you’d think if designing a container to block out light (which is also electromagnetic radiation) or to be waterproof.

So don’t, for example, go to Harbor Freight and buy a ‘stainless steel tool chest’ that actually only has some very thin pieces of stainless steel in the center of some of the tool chest’s sides, and plenty of plastic elsewhere. It might be a great way to carry tools, but it is not useful as a Faraday Cage.

Faraday Cage Construction 2 – The Need for Good Electrical Joins

So maybe you’ve ended up with an enclosure that is metal on all sides. That’s good, but there’s more to it than that. Are all the sides connected to each other electrically? If they are not, you again have a wave guide or possibly a radiation ‘concentrator’ rather than some sort of blocking cage, and might end up with worse outcomes than without an enclosure at all.

Make sure there is no varnish or other ‘invisible’ insulation on each of the metal surfaces. And have good connections on all sides, as much as possible, so that the shortest physical distance from any point to any other point on the enclosure is also the same as the shortest electrical distance. As soon as you start to require the radiation to go ‘the long way around’, you start to tempt it to take ‘a shortcut’ through the container rather than around it.

In simple terms, if you have a cube type shape, that means that each of the six sides of the cube should be physically and electrically connected to other sides of the cube on each of its four edges. A ‘press fit’ is acceptable only if the two surfaces are each clean and not corroded (both dirt and corrosion are usually insulators rather than conductors). You’ll of course have welded or soldered joins on most of the sides of the enclosure, with just its ‘lid’ being openable in some form, and you need to be sure that all four edges of the lid provide a positive seal and electrical connection.

An Essential but Usually Overlooked Requirement with Metal Tape

Now for an important consideration. If you are sealing some sort of container, you probably know or can guess that you should use a metal foil type of tape to seal the container with. Okay, but there’s a trick that many people don’t think through. The typical adhesive on generic metal foil tape acts as an insulator. It insulates the tape from whatever you are taping it onto, and also insulates the tape from itself (if you have tape overlapping itself). This makes the metal foil tape close to useless.

Be sure to get tape that has conductive adhesive on it. Needless to say, Amazon is your friend, and offers a wide range of different types of metal foil tape with conductive adhesive on it, as you can see from the link. Better still, the material isn’t very expensive.

Do You Need to Ground Your Faraday Cage?

This is one of the most widely misunderstood aspects of Faraday Cage design and construction. Faraday cages do not need to be grounded, indeed, as best we vaguely remember our advanced college physics classes, they should not be grounded.

You’ll see many prepper sites that say you should ground a Faraday Cage, but they either don’t say why, or say ‘to bleed off the charge’, or perhaps work on the semi-stated assumption that you ground other electrical things for safety and so, therefore, you should also ground a Faraday Cage. This is all wrong. Faraday Cages do not accumulate charge. They simply allow a charge to pass from one side of them to the other, without passing ‘through’ the inside of the cage.

That process also points to why you should not ground a Faraday Cage. If you ground the cage, it is no longer an isolated part of normal space that just so happens to be better conducting than the space inside it. Now it has become an antenna of sorts, and even can be considered as a ‘magnet’ for the radiation. Think of the process like a lightning rod – a lightning rod actually works by attracting lightning – it ‘pulls’ the lightning to itself rather than allowing the lightning to semi-randomly choose anywhere else to land. The last thing you want is to change from a neutral Faraday cage to an active receiver of the radiation! Instead of the EMF passing around your object, it now goes onto the object and travels along it and down to the ground.

Like all antennas, a grounded Faraday cage ceases to be a conductive material and instead starts to become a resonating material with inductive and capacitive properties, with some parts of its length having high resistance (impedance) and thereby potentially defeating the major concept of the cage – its ability to more effectively transfer EMF around its exterior rather than through its middle. It will be itself absorbing and re-radiating some of the EMF it is now ‘receiving’ and conducting, and while we’re not exactly sure, we fear some of that transmission may be into itself and whatever is inside.

Think of it this way. Planes get struck by lightning dozens of times every day, but nothing happens to them because the planes are essentially Faraday cages. The lightning strikes the plane, travels around/through it, and then keeps on going. But imagine if the plane had a big long antenna trailing off the end of it, all the way down to where it was dragging along the ground. Now the plane has changed from being an electrically neutral thing that the lightning doesn’t ‘see’ or expend energy on, and instead becomes a huge big ‘magnet’ that draws lightning from miles around to it.

‘Nuff said? Don’t ground your cage. Not only don’t deliberately ground it, but also keep it away from any ‘accidental’ grounds – for example, don’t have it resting on solid earth or attached to any metal beams that might lead to the ground, and – whatever you do – please don’t have any electric wiring feeding into it!

Insulating the Contents from the Cage Walls

Something we often see overlooked in articles about Faraday cages is the need to insulate the contents from the cage walls. When the cage is actually ‘doing its job’, those walls – both inside and outside the cage – are going to be alive with energy, and that energy will be eager to find anything and everything to flow into and fill.

If you think about what would happen if you had the contents actually touching the walls, there’s a chance you’d end up creating an electrical path through the cage that would be easier or almost as easy for the radiation to travel along as it is for the radiation to go around the outside of the cage. The last thing you want to do is to encourage the radiation to come into your cage and move around.

We suggest you simply line the inside of your cage with thin foam – perhaps 1/4″ – 1/2″ thick. That’s all you need to do – have some sort of light simply stand-off that keeps your electronics off the walls of the container.

Testing Your Faraday Cage

There are several ways you can test your Faraday Cage once you’ve constructed it. Go somewhere with a very strong cell phone signal (such as right next to a nearby cell tower) and confirm you’ve all the bars on your phone showing max strength.

Put your phone in the cage and try calling it. If you hear it ring, you know you’ve got a problem.

Next, place a call from your phone to someone else, then put the phone in the cage and close it up. Does that cut off your call? If it doesn’t, you again know you’ve got problems.

Try this with the phone and cage oriented in different directions (and with the phone either vertical or horizontal inside), in case radiation can get in one way but not another way.

Another test is to check for electrical continuity all the way around the cage. With an ohm meter, set it on its lowest/most sensitive ohm scale and first calibrate it to zero ohms. Then stick the probes on random parts of the cage, and ensure that everywhere you place the probes, you’re getting under a 1 ohm resistance reading. Test a range of combinations from any side to any other side.

Those are the two easiest types of test to do. Happily, there’s not really much of a trick to building a cage, and so there’s every good chance your cage will pass these tests.

Summary

Build yourself a Faraday cage – perhaps out of plumbing ductwork type thin metal sheeting that is easy to work and not too ridiculously heavy. Follow the design considerations discussed above – perfect electrical and physical seal, nothing touching inside, outside not grounded, and you should have an effective way of protecting an essential set of spare electronic devices for WTSHTF.

The classic tube powered Collins 75A4 radio, now 50+ years old. Revered by some hams – but a good choice for you?

This is the second part of a two-part article about buying used gear. The first part discussed general considerations when buying any type of used gear, and how it is possible to be mislead and to end up buying junk you don’t need, while all the time thinking you’ve bought something useful at a bargain price, and closed with some suggestions and tips on how to bargain for the best possible price.

Now it is time to focus in on the special considerations relating to electronic equipment.

Age and Reliability

Just about everything has a finite life. The older a thing is when you buy it, the less remaining life it has. Even ‘your grandfather’s axe’ has a finite life – you have to keep replacing its head and handle every decade or two.

To make things more complex, ‘age’ is measured two different ways. The first aspect of age is the simple passing of time, no matter if the unit is being used or not. Some components age even when not being used. Rubber cracks, plastics lose their plasticizers, springs lose their tension, seals leak, wet things dry out (and dry things get wet) and so on. Rust never sleeps, right?

The second aspect of age is the number of hours the unit has actually been powered on and in use. Just about everything has a finite total number of hours of life – sure, sometimes that number might be very high, but it is still a number, and every minute anything is turned on, you’re steadily rolling the dice as the minute hand moves, each time hoping you don’t get an unlucky result and your equipment randomly failing.

There is a third element of age as well – the type of operation and environment. Something that has been run ‘hard’ at 110% of rated power will age massively more quickly than something that has been run carefully/gently at 90% of rated power. Something with a ‘dirty’ power supply is going to be stressed more than something with a nice clean stable power supply. Something that has been in a very hot environment will age very much more quickly than something that has been kept cool. Heat is the universal enemy of all electronic circuitry, and as a rule of thumb, for every ten degrees hotter that something is operated at, you are halving its life. Run it 20 degrees hotter, and you’ve reduced its life to one-quarter, and so on.

When you see something, you have no way of guessing about how the unit has been used in the past, and a product that is about to fail seldom gives you any sort of indication that is about to happen.

The simple passing of time affects electronics as much as it does anything else. A surprising but key aging element is corrosion – the oxidation of the leads on electronic components and the increasing difficulty of soldering them effectively to other devices, and the slow failure of existing soldered joins. The key factors here are not to store components in regular plastic bags, and to keep them cool and dry.

Regular plastic bags are thought to ‘outgas’ and ‘leach’ out chemicals that accelerate corrosion and harm the materials stored inside them. Barrier bags (a fancy way of saying ‘nylon’) are okay, and archival plastics probably are too, but regular PE type materials – best to avoid them. This is a good article about component storage.

Of course, moisture is an enemy and corrosion accelerant, so keep things as dry and humidity as low as possible. A related thing – bad news if you (or previous owners) live near the sea, with the higher salt levels brought in from sea spray.

Some things have obvious life-limiting factors as part of their design, and may be impractical to maintain. Other things have very long lives and are practical to maintain.

In the case of electronics, some items will wear out and fail semi-randomly, some will do so moderately predictably, and some will last almost forever. And it is all overlaid with an element of random chance. You’ve no way of knowing if your particular piece of gear will end up with a long life or a short life. The only thing you do know is that the more it is used, the closer it is getting to its ultimate failure.

Semi-conductor and Component Aging

If you have really old gear with tubes inside, then you need to plan for occasional replacements of the tubes. Just like incandescent light bulbs burn out, so too do tubes. But, unlike a lightbulb which burns more or less the same every day until suddenly failing, with a tube, it isn’t only just having it fail by sudden total burning out of the filament. Tubes also have several other factors that influence their longevity, and their performance steadily declines, every hour they are being used. The more they are used, the less remaining life they have, and the more poorly they will perform.

Most tubes will have a rated life stated on their specification sheet, and you’ll see this life expectancy can vary wildly. One make/model of tube might be rated for 1,000 hours, another for 10,000 hours. And, in all these cases, please be sure to understand what this rating means. A rating of 1,000 hours doesn’t mean ‘all these tubes will work perfectly for 1,000 hours and then fail some time after’. It means ‘some tubes will fail quickly, some will fail slowly, and on average, you’ll get about 1,000 hours overall’. That is a very different scenario, isn’t it – some tubes will start failing immediately.

Back in the days of early computers that used thousands of vacuum tubes for their logic, people were employed as a full-time job just going through the racks and non-stop replacing tubes.

There’s another factor with tubes, too. Unfortunately, ‘new old stock’ tubes might already have some percentage of their working life used up, just by sitting on the shelf (for example, if the vacuum seal is less than perfect). If you are able to test your tubes on a tube tester, that will show you where on the spectrum each tube lies as between brand new and into the failure zone.

The solid-state components – the transistors and integrated circuits – will fail semi-randomly. There is an initial period that is sometimes termed ‘infant mortality’ where new components might fail, then there’s a long period of reliability where failures are random and rare, then beyond that, the failure rate starts to inch up again. The steady declining performance of vacuum tubes is not as pronounced with solid state devices, although it is present, but to a much more subtle degree.

Interestingly, and sadly, the newer and more modern the solid state devices, the faster they will fail. Increasing miniaturization makes even individual atoms and molecules significant elements in an integrated circuit, and gradual effects such as the migration of materials across substrate barriers are much more significant in miniaturized components than in earlier items that were hundreds of times larger. The tolerance range between operating voltages and maximum voltages is also greatly reduced in modern semiconductors.

There’s not a lot you can do about that, though, but just because a neighbor has a 50-year-old radio working perfectly absolutely does not guarantee that the new radio you buy tomorrow will outlast it. Similarly, as you read around the internet and prudently do your research, be sure to understand that the people who confidently point to very long life with their electronics are probably, and by definition, talking about old gear. When you think about it, it is impossible to say ‘my radio has worked perfectly for 50 years’ when you are talking about a radio you bought just last year, isn’t it! But if you search out some of the technical papers about semi-conductor longevity, you’ll see the ugly truth that the smaller the componentry, the more delicate it is and the shorter its life. This is also a factor in terms of EMP vulnerability – an electronic component designed for 2 volt logic and within a thousandth of an inch of the next component on the same chip is going to be fried by an induced 5 volt power surge which can also pass across the tiny gap between it and the next component, whereas an old transistor, 100 times larger in size, and working off 12 volts, will laugh at a 5V surge and not even notice it.

Resistors have a long life, particularly if they are newer metal film rather than older carbon film. Older style carbon film resistors are cylindrical in shape and usually have a dark brown body; newer metal film resistors are a lighter brown color and typically are ‘bar bell’ shaped – cylindrical but of larger diameter at each end.

And inductors – coils of wire – last about as close to ‘for ever’ as anything ever does.

The ‘Achilles Heel’ of most electronics are the electrolytic capacitors. These can dry out (or leak) and generally have a life somewhere between 10 – 40 years. Some people replace all their electrolytic capacitors every 10 – 20 years, whether they need to be replaced or not, particularly because if a capacitor fails, it can cause cascading problems throughout the circuit including the failure of power transistors and other costly/hard to replace components.

Batteries – Both Obvious and Obscured

Perhaps the most regularly replaced item in any piece of electronics are the batteries. And, in considering this, don’t forget that many electronic items have both the obvious/main battery, but possibly also some other obscured/hidden batteries that are used to do things such as storing the device’s settings in memory so that it doesn’t reset every time you turn it off. These tiny batteries are invariably overlooked until they fail, so if you are buying any used equipment, it is a good idea to ascertain if they have such secondary batteries and then to replace them if they exist.

A regular rechargeable battery has a very variable life, depending on the conditions in which it has been used, stored, and recharged. Unless you have special test equipment, and also know the expected values for an optimum conditional representative unit, you can’t really check to see what state of health the batteries are – better to play it safe and treat all batteries as nearly at the end of their lives.

On the other hand, the good news about most rechargeable batteries is that their ‘life’ isn’t defined by a sudden total failure. Instead, it is just a steady decline, with each subsequent recharge storing less power than the one before, until you get to a point where it is no longer convenient to keep recharging a battery that takes two hours to recharge and then runs for 30 minutes (or whatever). So in a Level 3 situation, you’d keep using batteries long past the point you’d swap them.

On the other hand, rechargeable batteries can indeed also fail completely, and not hold any charge at all. All the more reason to replace all rechargeable batteries (or at least to buy a spare set and store them until needed) when you buy used electronic equipment.

Maintainability

So maybe something fails in the electronic item you purchased. Can you trouble-shoot to find the failure, and can you then fix it? Years ago, the answer was ‘yes’ – large-scale discrete components, individually soldered to spacious printed circuit boards, were easy to replace, and when something failed, you only needed to replace that one thing.

But now, with tiny SMD components less than half the size of a grain of rice, the ability to troubleshoot and replace is much more complicated than it used to be, and requires a steady and skilled hand and soldering iron. ICs might contain millions of transistors, so a single transistor failure might take the entire IC out of service. That is okay if you have spare ICs, but pretty soon, you’ll find you are spending more to build an inventory of spare parts than you are on the gear to start with. Another difference is that whereas before, it was practical to have a spare parts inventory of all the different resistor, inductor and capacitor values, plus a smattering of the most common diodes and transistors, these days, most products have their own unique integrated circuits so you must have spares for each item rather than a common inventory of spares for everything.

This is also a reason to standardize. Rather than having a dozen different walkie-talkie radios, for example, buy twelve (or thirteen or more) the same. If one fails, you then use it as spare parts for the others. This also makes it enormously easier from an operational perspective if everyone has the same gear. So that ‘really nice’ and inexpensive piece of gear you’re drooling over has to be considered in the context of the practicality of requiring people to learn how to use a different interface, and the need to keep a separate inventory of spares for it. Better to use the money to buy another one of the standard model units you already have.

The Future Lifespan You Need

An interesting consideration is to decide how long you need something to last in order to have received fair value from it. Of course, ideally, everything would last for ever, and equally ideally, we’ll never experience an event that forces us to resort to our emergency equipment and supplies. The world would just continue on, the same as it has been until now.

But both those scenarios are sadly unrealistic!

Should we consider it as good news or bad news that many of us have been prepping, to some degree or another, for more than two decades? Is your glass half-full or half-empty? Are you upset if at the end of a year, you’ve not filed any claims on your car insurance policy? Do ten or twenty years with no need to activate your preps make next year riskier or safer?

The point behind these (largely unanswerable) questions is that much of the stuff we’ve bought to have for a possible future WTSHTF situation are things we’ve now owned for ten years or longer. If we bought something that was already 10 – 20 years old when it was purchased, it would therefore of course be up to 30 years old now, and at the point where it would be prudent to think about replacing (or at least giving it a thorough overhaul and replacing many of its components) – or possibly supplementing it with a new set too.

In other words, if you are buying something today that you need to use tomorrow and which will have paid for itself in terms of value and use within a year or so, it doesn’t really matter if its life is two years or twenty years (although of course twenty years would be nicer!). Your main focus is on an item that will work reliably today and for a long enough period so that it has paid for itself by the time it fails and you replace it.

But if you’re buying something that you won’t even touch for a decade or two, you need something that will be able to sit in storage for that period of time, and then be activated and work for another decade or two or however long you expect to need to rely on it.

This issue – that if you buy something old today, it might be very old by the time you finally get to use it – is another reason to avoid buying old stuff unless you know how to maintain and repair it and have an inventory of the necessary spares to do exactly that.

What We Do

We don’t buy anything essential that was made before 2000 (mainly because it is a nice round number to use as a cut-off) and we generally prefer to buy things that are less than ten years old, unless there is a special reason to choose something older.

And whenever we can cost-justify it (which is most of the time – not because we have lots of money, but simply because the cost/value/benefit equation supports it) we prefer to buy brand new gear, run it for a few months to check for any ‘infant mortality’ and then put it in extended storage until needed.

Part One of This Article

This is the second part of a two-part article. If you’ve not already done so, you might like to also read the first part, which talks about buying used/second-hand gear in more general terms.

The HP-12C – possibly the finest calculator ever and still being made by HP.

So, after TEOTWAWKI, what happens when we need to do ‘figuring’ – to do some sums, to calculate some values? Our computers are dead, our notepads fried, and our calculators have run out of batteries.

We have several suggestions that will make your life easier.

Solar Powered Calculators

Our first suggestion is to stock up on calculators that use photo-electric cells to power them. These can be expected to last for probably 15 – 25 years, maybe longer, and if you store them in a cool dryish sort of place that gets neither extremely hot nor cold, that will be a good environment for longest life. Solar powered calculators are inexpensive, lightweight, and not very large (but note that larger ones are easier to operate and you’re less likely to make errors entering numbers, and have easier to read screens). Amazon sells a broad selection, many at less than $10 each. You want to choose display only calculators, not printing calculators – the printing calculators use a lot more power, plus you then need rolls of paper and ink ribbons too.

We recommend you store two or three solar-powered calculators in your Faraday Cages. Take them out, one at a time, if you need to have one readily accessible.

HP-12C

The second is to get one of the brilliant Hewlett-Packard HP-12C calculators – in our opinion, the finest calculator ever made. Not only can this calculate just about anything and everything you’d ever want to calculate, but its batteries last almost literally forever. The record is currently an HP-12C with batteries that are now 22 years old, and it is still going strong. In other words, the limit is more the storage life of the batteries than the power used by the calculator – we regularly get 10+ years of life out of each set of batteries we use (although with the new non-mercury type silver-oxide button batteries, we suspect their ‘shelf/storage life’ is not as lengthy as with the earlier mercury batteries – we’ve seen figures claiming five years for silver oxide in place of ten years for mercury batteries – yet another case where Congress has legislated a good product out of existence for the thinnest of reasons).

The HP-12C design is now over 30 years old, but it was so perfect when it first came out that customers have resisted every attempt by HP to modernize or replace it. The closest to a replacement is the latest ‘Platinum edition’ version of the HP-12C, and you can interchangeably get a regular or a Platinum version; the differences are trivial and mainly ‘under the hood’.

The only thing to be aware of is that there’s something missing from the classic HP-12C calculators, and obscured on the Platinum edition versions. The equals sign. The calculator uses a different way of calculating – you key in the first number then hit the Enter key, then you key in the second number, then you press whichever function key you wish for adding, subtracting, multiplying and dividing, as well as very many other functions too. This is called ‘RPN’ or Reverse Polish Notation; it takes a bit of getting used to but is actually surprisingly logical and simple.

We own several of these calculators; they are robustly built and never seem to break. The best thing about the RPN keyboard is always seeing the puzzled look on other people’s faces. ‘Can I borrow your calculator?’. ‘Ummm, yes, sure’ we say, unenthusiastically, maybe adding ‘it is a bit complicated to use’. But our disclaimer about it being complicated is always ignored. Then, invariably, two things happen. ‘How do you clear it’ and ‘Where is the equals sign’, followed, a minute later, by the borrower handing it back to us! This means that we’ve never lost a calculator by someone ‘borrowing’ it and ‘forgetting’ to return it! They cost $50 – $60 each these days (used to be more) so we’d rather not have them disappear.

You might also want to consider an HP-11C ‘scientific calculator’ – most of the extra functions on a 12C are financial; if you think you might need some trigonometry functions in particular (useful in surveying and building) then get an 11C too.

Again, keep your HP-12C in a Faraday cage until you need to deploy it.

This shows the stylus and the clearing bar that come with an Addiator adding/subtracting device.

Mechanical Adders

Now it is time to go lower tech. There are two low tech solutions to consider, one being better than the other.

You should consider getting a hand-operated adding machine. You might immediately think of some of the large boxy machines that used to sit on accountants’ desks – quite possibly with a roll of paper coming out the end as well, and a handle that the user would pull towards them to enter each number.

Those are great units, but you’re going to run out of rolls of paper and ink ribbons very quickly, so we don’t recommend them for a Level 3 type scenario. However, there’s another more subtle challenge to them, too. They have dozens, or even hundreds of moving parts, and that’s a lot of things to go out of adjustment, springs to break, or in some other way to have something fail.

Slightly simpler, and generally older, are machines that simply display the running total in a window rather than print on a piece of paper. Some look like ‘regular’ adding machines, others are more complicated and can be used for multiplication as well as addition.

While it is a long time since machines such as the American Rapid Calculator Co pinwheel adding machines were made, the Soviet Union made similar machines called a Feliks brand Arithmometer. I’ve seen them dated from the 1930s to the late 1970s – they stopped production in the early 1980s and one of those might be worth considering. But be aware that although they look to be very solidly built, like much in the Soviet era, that is as much illusion as reality. It is reported that the gears inside are made of low quality zinc. As a bit of trivia however, the name ‘Feliks’ is the first name of Felix Dzerzinsky, the first head of what became the KGB, and were originally made in a factory in Moscow that subsequently became the KGB headquarters (on Lubyanka Square).

Some of the German machines (eg Thales up to the late 1960s and Brunsviga) are not all that old, either. All these ones that look similar spring from the same design, originally by a Swedish-Russian man in St Petersburg.

Make sure you’re getting a non-electric machine, though. There are lots of Monroe type adding machines that look manual but are electric, and can be trouble-prone and very difficult to repair. If you’ve ever seen one of those working, you’ll immediately understand how the moving parts are considerably stressed as it crashes and clatters its way through to a solution.

There’s an even simpler solution that is as close to fail-proof and fool-proof as it gets. An Addiator. These units are tiny (about 2″ x 6″ x 0.5″), weigh only a couple of ounces, and are totally simplistic to use with almost nothing to break or go wrong. They can easily be found on eBay and elsewhere, probably costing no more than $10 – $20 a piece. Search for ‘Addiator’ or ‘Arithma’ on eBay – we just did and found 44 listings. Make sure the unit comes with its stylus – other things can be used instead of course, but if it has its stylus to start with, so much the better.

Addometers are slightly less common and more expensive, and not quite as intuitively obvious to use.

Other similar products exist, for example, the Sterling Dial-a-matic. Pick and choose whichever style you like, they’re all reasonably reliable and very easy to use.

Make sure that the unit you select has a lot of digits – ideally eight or more, so you can add up reasonably large numbers. We’ve seen Dial-a-matics with as few as four, which is hardly worth the hassle of buying, owning and using. Also make sure the machine can subtract as well as add (as best we can tell, the Resulta mini adding machines won’t subtract).

Slide Rules

Many people say the Faber Castell 2/83N slide rule is the best ever made. Last produced in 1976, but still available on eBay and elsewhere.

So your Addiator will see you right for adding and subtracting. But what say you need to multiply or divide – or, even worse, to work out square roots, or do trigonometry?

Until the early 1970s, everyone used slide rules for such things. Sure, they don’t have eight glowing digits of instant and near perfect accuracy, but for a century or more, slide rules were used to calculate and build everything, even jet planes and rockets. The happy reality is that most of the time, we don’t need eight significant digits, and rather than being ‘significant’, most of them are illusory because the measurements we are feeding in to our calculators are imprecise to start with.

Some slide rules might still be manufactured, new, in China perhaps. But we suggest that the best approach is again to go to eBay and pick up one from there – they have an entire section dedicated to slide rules. We’ve seen good slide rules sell for $20 – $40. You want to get one that is 10″ in length, not the half sized ones, and not the double sized ones. Make sure it isn’t missing its cursor (the clear plastic thing that slides along it), and the more scales it has, the merrier. The very best slide rules have a pair of ‘folded’ scales that in effect give you the benefit of a 20″ rule without any of the attendant disadvantages – one scale set goes from about 1 – 3.2 and the second scale set goes from about 3.2 – 10, and easy set has more graduations to give you a bit more accuracy. We know that some of the double-sided Faber Castell slide rules (ie the W scales on the 2/83 and 2/83N rules) have these folded scales, and some of the other brands have them on their high-end slide rules too.

Other than these considerations, you can’t really go wrong with any of the different brands or models.

Ideally if it comes with instructions (and in English – some of the slide rules are sold from other countries and their instructions aren’t always in English) that will save you from any need to buy a book on how to use a slide rule, too.

Giving you the best of both worlds, the German company Faber Castell bought the Addiator adding machine company and made combo units – slide rule on one side and Addiator on the other. Some of them are still available.

The Ultimate in Low-Tech Calculating?

So, there you are with your Addiator and slide-rule (as well as a solar-powered calculator and perhaps even an HP-12C). You’re all set to calculate whatever the future holds, right?

Yes, you probably are. But if you wanted to regress back one further step in calculating, you could always get an abacus too. A skilled user of an abacus can do calculations almost as quickly as a modern person with a calculator, but it does require skill and practice/training to become that proficient.

So you might decide to pass on that for now, but if you want to be totally prepared for everything, get a book on how abacuses work so you can simply build your own if needed in the future, and have the information you need for how they work.